public class Test {
    //大数加法
    public String solve (String s, String t) {
        // write code here
        int i = s.length() - 1;
        int j = t.length() - 1;
        int carry = 0;
        StringBuffer stringBuffer = new StringBuffer();
        while(i >= 0||j >= 0||carry !=0){
            int x = i < 0?0:s.charAt(i--) - '0';
            int y = j < 0?0:t.charAt(j--) - '0';
            int sum = x + y + carry;
            stringBuffer.append(sum % 10);
            carry = sum / 10;
        }
        return stringBuffer.reverse().toString();
    }
}
